When you send a post, it goes to a relay for storage and delivery. You don’t have to edit the relay, you have to get a relay to edit the data. If you own your relay, trivial.

If you rely on someone else’s relay, now it’s negotiation time.

If you’d rather use some centralized service and just ask mark zuckerberg to do it, then that’s fine too.

Once you mail a letter, you can’t edit it. Proof read before posting.